The present invention relates generally to a printer, and more particularly to a printer of the type using thermal print ribbons, carbon film ribbons or other disposable or "one-time" ribbons which, once used, cannot serve any more.
Printers known in the art are designed such that a ribbon cassette or cartridge is either movable together with a print head while being supported by a carriage, or alternatively fixed to a frame of the printer and not movable. A printer according to the invention is of the latter type wherein printing is effected with a stationary ribbon cassette.
In a known printer of such a type with a stationary ribbon cassette loaded wth a disposable ribbon, an active length of the ribbon extends from a ribbon feed section (feed spool) of the cassette to a ribbon take-up section (take-up spool) of the cassette, along the length of a platen. A print head is moved along the platen to print a line of characters via the active portion of the disposable ribbon in front of the platen. Upon completion of printing of each line of characters, the disposable ribbon is fed by a distance equal to a predetermined length of a printing line, which is interpreted to mean a distance between preset right and left margin positions. In an ordinary printing, each line is not printed over its entire length. For example, some of the lines to be printed are indented (e.g., the first line of a paragraph), and most of the lines are followed by a plurality of successive spaces (the last line of a paragraph, in particular). That is, some lines of characters begin or end with a certain length of blank left after or before the preset margin positions. For such printing lines, the active portion of the disposable ribbon is not used over a distance equal to the length of the blank (successive spaces). This unused portion of the ribbon is taken up by the take-up spool, without serving for printing. Thus, the known printer with a ribbon feed arrangement as discussed above suffers a waste of a disposable ribbon, and is not satisfactory in terms of printing economy.